The two main types of energy devices can include energy storage devices and energy generating devices. Examples of the energy storage devices can include electrochemical capacitors and batteries. Examples of the electrochemical capacitors can include an electric double layer capacitor and a pseudocapacitor. The electric double layer capacitor can use an activated carbon as a polarizable electrode and can utilize an electric double layer formed at an interface between a pore surface of the activated carbon and an electrolytic solution. The pseudocapacitor can use a transition metal oxide, whose valence continuously changes, and an electrically-conductive polymer which can be doped. Moreover, two main types of the batteries can include a secondary battery, which can be charged and discharge by utilizing intercalation and chemical reactions of active materials, and a primary battery, which is not rechargeable after being discharged once.